Automatic focusing systems are known which use photo sensitive cells to determine whether the optical system for a camera is correctly focused. Such photo cells are used with a dithered signal from the subject; in such systems a peak signal is indicative of proper focus and may be used to adjust the camera lens. The photo sensitive materials necessary for such automatic focus systems present a problem with conditions of low level light emanating from the subject. The response time of the automatic focusing system photo sensitive cell is slowed causing a delay in the transmission of the peak signal. Such a delay is not incurred when the light levels are adequate as the response time of the photo sensitive cell is acceptable under such conditions.
It is therefore an object of the invention to provide an automatic focusing system which includes a system by which the delay incurred during sensing of the subject in low light conditions is corrected to provide a proper signal for focusing.